Location: Agroecosystems Management ResearchTitle: Methods to create thermally oxidized lipids and comparison of analytical procedures to characterize peroxidation Author
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2014
Publication Date: 7/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59411
Citation: Liu, P., Kerr, B.J., Chen, C., Weber, T.E., Johnston, L.J., Shurson, G.C. 2014. Technical note: Evaluation of methods to determine peroxidation of lipids. Journal of Animal Science. 92:2950-2959. Interpretive Summary: Measurements of lipid peroxidation provide important information in assessment of lipid quality which is important because of the potential impact on animal health and performance due to the effects of secondary and tertiary peroxidation products. Unfortunately, the assessment of the degree of lipid peroxidation is challenging because of the drawbacks of each method used. The results of this research suggest that there is no single method that seems to adequately describe or predict lipid peroxidation due to the complexity of lipid composition and the phases involved in lipid peroxidation. Research results described in this report provides scientists at universities, feed companies, allied industries, and livestock production facilities information from which to fully evaluate lipid peroxidation, and the relationships between different peroxidation analyses.
Technical Abstract: The objective of this experiment was to evaluate peroxidation in 4 lipids, each with 3 degrees of peroxidation. Lipid sources were: corn oil (CN), canola oil (CA), poultry fat, and tallow. Peroxidation levels were: original lipids (OL), slow-oxidized lipids (SO), and rapid-oxidized lipids (RO). To produce peroxidized lipids, OL were either heated at 95 degrees C for 72 h to produce SO, or heated at 185 degrees C for 7 h to produce RO. Five indicative measurements [peroxide value (PV), p-anisidine value (AnV), thiobarbituric acid reactive substance concentration (TBARS), hexanal concentration, 4-hydroxy nonenal concentration (HNE), and 2,4-decadienal (DDE)] and 2 predictive tests [active oxygen method stability (AOM) and oxidative stability index (OSI)] were performed to quantify the degree of oxidation of the subsequent 12 lipids with varying degrees of peroxidation. Analysis showed that a high PV accurately indicated the high degree of lipid peroxidation, but a moderate or low PV may be misleading due to the unstable characteristics of hydroperoxides as indicated by the unchanged PV of rapidly oxidized CN and CA compared to their original state (OL). However, additional tests which measure secondary peroxidation products such as AnV, TBARS, hexanal, HNE, and DDE may provide a better indication of lipid peroxidation than PV for lipids subjected to a high degree of peroxidation. Similar to PV analysis, these tests may also not provide irrefutable information regarding the extent of peroxidation due to the volatile characteristics of secondary peroxidation products and the ever changing stage of lipid peroxidation. For the predictive tests, AOM accurately reflected the increased lipid peroxidation caused by SO and RO as indicated by the increased AOM value in CN and CA, but not in poultry fat and tallow, which indicates a potential disadvantage of the AOM test. Oxidative stability index successfully showed the increased lipid peroxidation caused by SO and RO in all lipids, but it too may have disadvantages similar to AnV, TBARS, hexanal, DDE, and HNE because OSI directly depends on quantification of the volatile secondary peroxidation products. To accurately analyze the peroxidation damage in lipids, measurements should be determined at appropriate time intervals by more than one test and include different types of peroxidation products simultaneously.